Hi there i am putting a big system in my car so just wanted some advice with installing a volt meter.. If i connect it directly to the battery it will drain the battery is there any other way i can connect it so when i take the key off the volt meter goes off?...

You have two electrical feeds for your car.

One that is permanent for things such as the clock and alarm. You also have a feed which only provides a current when the ignition is on for the radio for example. Not sure exactly how the voltmeter wires up, but you may be able to wire it to the ignition feed so it turns off with the keys.